Snake oil is a traditional Chinese medicine used to treat joint pain. However, the most common usage of the phrase is as a derogatory term for compounds offered as medicines which implies that they are fake, fraudulent, quackish, or ineffective. The expression is also applied metaphorically to any product with exaggerated marketing but questionable or unverifiable quality.
Snake oil originally came from China, where it is called shéyòu (蛇油). There, it was used as a remedy for inflammation and pain in rheumatoid arthritis, bursitis, and other similar conditions. Snake oil is still used as a pain reliever in China. Fats and oils from snakes are higher in eicosapentaenoic acid (EPA) than other sources, so snake oil was actually a plausible remedy for joint pain as these are thought to have inflammation-reducing properties. Snake oil is still sold in traditional Chinese pharmacy stores.
Snake fat also played a role in ancient Egyptian medicine, mixed with the fats of lion, hippopotamus, crocodile, tomcat, and Nubian ibex into a homogenous mass believed to cause bald men to grow hair.
Chinese labourers on railroad gangs — involved in building the Transcontinental Railroad to link North America coast to coast — gave snake oil to Europeans with joint pain. When rubbed on the skin at the painful site, snake oil was claimed to bring relief. This claim was ridiculed by rival medicine salesmen, especially those selling patent medicines. In time, snake oil became a generic name for many compounds marketed as panaceas or miraculous remedies, whose ingredients were usually secret, unidentified, or mis-characterized — and mostly inert or ineffective, although the placebo effect might provide some relief for whatever the problem might have been.
Patented snake oil remedies actually originated in England, where a patent was granted to Richard Stoughton's Elixir in 1712. Since there was no Federal regulation in the USA concerning safety and effectiveness of drugs until the 1906 Food and Drugs Act, and various medicine salesmen or manufacturers seldom had enough skills in analytical chemistry to analyze the contents of snake oil, it became the archetype of hoax. American snake fats do not have EPA contents as high as those of the Chinese water snake. The American snake oils were not effective in relieving pain like the original Chinese snake oil — further promoting the hoax stereotype.
The snake oil peddler became a stock character in Western movies: a travelling "doctor" with dubious credentials, selling some medicine (such as snake oil) with boisterous marketing hype, often supported by pseudo-scientific evidence, typically bogus. To enhance sales, an accomplice in the crowd (a "shill") would often "attest" the value of the product in an effort to provoke buying enthusiasm. The "doctor" would prudently leave town before his customers realized that they had been cheated. This practice is also called "grifting" and its practitioners "grifters".
The practice of selling dubious remedies for real (or imagined) ailments still occurs today, albeit with some updated marketing techniques. Claims of cures for chronic diseases (for example, diabetes mellitus), for which there are reputedly only symptomatic treatments available from mainstream medicine, are especially common. The term snake oil peddling is used as a derogatory term to describe such practices.
An alternate theory for the origins of the term "snake oil" is that it was a corruption of "Seneca oil". The Senecas, a tribe in the Eastern United States, were known to use petroleum from natural seeps as a liniment for skin ailments. However, Native Americans are known to have used rattlesnake fat and the herb snakeroot for various purposes.
The composition of snake oil medicines varies markedly between products.
The Chinese water snake (Enhydris chinensis) is the richest known source of EPA, the starting material the body uses to make the series 3 prostaglandins. These prostaglandins are the biochemical messengers which control some aspects of inflammation, rather like aspirin which also affects the prostaglandin system. Like essential fatty acids, EPA can be absorbed through the skin. Salmon oil, the next best source, contains 18% EPA. Rattlesnake oil contains 8.5% EPA.
Stanley's snake oil – produced by Clark Stanley, the "Rattlesnake King" – was tested by the federal government in 1917. It was found to contain:
(Note that this makes the above similar in composition to modern-day capsaicin-based liniments. Thus, this early snake oil may have worked somewhat as intended, even if it did not contain its alleged ingredients.)
From a purely pharmacochemical perspective, it is likely that the genuine Chinese snake oil is not fraudulent, at least for its intended purpose, since EPA indeed is an effective anti-inflammatory agent. On the other hand, American products made from rattlesnake fats, which have at most 1/3 of the EPA concentration of Enhydris chinensis fat, are likely to have been inferior or even useless for similar purposes because of their lower or even nonexistent anti-inflammatory contents — Stanley's snake oil contains no EPA at all. 19th century snake oil peddlers and apothecarians seldom had any serious knowledge of chemistry or pharmacology. It is likely that they did not understand the action mechanism of the Chinese product, or even know its functional ingredient. Instead of analyzing and reverse engineering the authentic remedy, they tried to imitate it with unimpressive results. Such inferior or even fraudulent products gave snake oil the reputation it has today.
English musician and comedy writer Vivian Stanshall satirized a miracle cosmetic as "Rillago—the great ape repellent"